the only option left is to connect an ammeter (20Amp) in series with
the positive of the battery and check the current consumptions using the
original square wave design as well as our PWM design. The difference
should instantly surface out.
there's a difference in the consumptions, because current is the key
factor that's causing the mosfets to blow.
circuit drew 2 amps, then I substituted the PWM circuit and it drew 14 amps and
blew one of the MOSFETS.
Mosfet Basics and I read "
1/10th of collector current is required for the current controlled device (BJT).
a voltage controlled MOSFET is a
2. Unipolar device - majority carrier device - fast switching speed
4. Forward voltage drop with positive temperature coefficient - easy to use
So this thing is telling that Mosfets are a Voltage controlled device.
Just to reiteriate my results from your Current draw test, my
Square wave circuit had 2 Amps draw with nothing plugged in to the
Inverter. PWM circuit Draw was 14 amps for just a second then it blew one
of the Mosfets.
One other Observation , when I power up the Square wave
circuit portion of our complete PWM circuit, the voltage at the Clock Output is
+6.10V. Now when I plug the circuit back into the PWM portion of our
circuit and POWER UP both circuits, the Voltage at the Transistor
Output to the Gate of the Mosfet was + 8.45V. Are these readings
shedding any light. Could it be because the voltage is too high at the
My original Square wave circuit has a voltage of +6.09V at the Clock
Output to the Mosfets Gate.
Mosfets do not depend on current triggers unlike transistors and therefore get fully triggered even with minutest current at their gates.
With the present situation I think we can try out the following things:
a car headlight lamp in series with the positive of the battery. This
will stop the mosfets from blowing-off and also its glow will instantly
inform you regarding the current consumption of the unit with the two
Next take a pot of 10K (DUAL) and connect its leads appropriately across the base and the ground of each transistor.
ON the power, adjust the pot, keeping a close watch over the glow of
the bulb, try to make its glow as close as possible to that of your
square wave design, you may also connect an ammeter in series with the
bulb to accurately manage the current while adjusting the pot.
Let's see what happens with the above procedures.
point, when you said " try to make its glow as close as possible to that of your
square wave design " not sure what you mean by this ?
To be Continued